In a holder device utilizing a pressure medium, a grasping portion for grasping a cutting tool is formed thin to promote its deformation whereas a support portion is formed thick to minimize its deformation for the sake of pressure loss prevention. In this way, an outer diameter of the support portion of the holder device is increased relative to a shaft diameter of a cylindrical portion of the cutting tool. However, this increased outer diameter of the support portion relative to the small-diameter cutting tool tends to invite interference when a narrow groove shape of an object is to be machined.
As an example of the holder device utilizing the pressure medium suitable for such a long and thin structure, there is known the holder device including a pressure guide arrangement for transmitting a supplied pressure along an axial distance between a pressure chamber and a pressure generator, the guide arrangement being formed of a sealed gap or passageway which is provided concentrically and annularly relative to a chuck axis line (see Patent Document 1).